Postpartum Anemia Is More Common and Lasts Longer In Poor Women Than in Those Who Are Better-Off

Between four and 26 weeks after giving birth, roughly one in four low-income women suffer from anemia; the proportion reaches nearly half, however, among those who were anemic during pregnancy and among black women. These findings, based on data for women enrolled in a federally sponsored nutrition program in 12 states,1 suggest a sharply higher prevalence of anemia among low-income women than has been found elsewhere among their better-off counterparts. They also indicate that although women's iron levels (which drop during pregnancy) typically recover 4-6 weeks after delivery, low-income women remain at risk of suffering from anemia for a substantially longer period. Consequently, standard screening protocols, based in part on the 4-6-week time frame, may be too limited to detect this condition in low-income women.

To determine the prevalence and predictors of postpartum anemia among low-income women, researchers gathered data on participants in the Special Supplemental Food Program for Women, Infants and Children (WIC) in 1996. The data, culled from a large-scale nutrition surveillance system, included nearly 60,000 women who entered WIC while they were pregnant, had a live birth and visited a WIC site once during the postpartum period. For this study, the researchers defined the postpartum period as 4-26 weeks after delivery, because maternal hemoglobin levels, which are reduced during pregnancy, should return to normal within this interval. Participants were predominantly non-Hispanic white (65%), unmarried (60%) and in their 20s (57%); the majority (64%) were high school graduates.

Twenty-seven percent of the women were anemic when they made their postpartum visit to WIC. At any given interval since delivery, the proportion who were anemic was at least 25%; it peaked at 29-33% among women visiting WIC 12-18 weeks after giving birth. The prevalence of postpartum anemia was highest among women who had been anemic during pregnancy (49%) and among black women (43% overall, including 48% of those who were 13-14 weeks postpartum). By comparison, 24% of women who had not suffered from prenatal anemia and 21% of white women had postpartum anemia.

In logistic regression analyses that controlled for the number of weeks since the birth and other factors that could contribute to the risk of anemia, prenatal anemia emerged as the strongest predictor of postpartum anemia: Women who had been anemic while pregnant had significantly elevated odds of postpartum anemia (odds ratio, 2.7). Compared with white women, blacks had more than twice the odds of postpartum anemia (2.3), and women belonging to other minority groups had about half again the odds (1.4-1.6).

A number of other variables had smaller but still significant associations with the risk of postpartum anemia. The odds grew with increasing prepregnancy body mass index and were significantly elevated for women aged 16-19, those who had had a multiple birth, women with no more than a high school education and those who were not married. Women who had been breastfeeding for more than three weeks had reduced odds of being anemic at their postpartum WIC visit (0.8 both for those who had been breastfeeding for 4-6 weeks and for those who had been doing so for longer).

The researchers note that the overall prevalence of postpartum anemia found in their study is dramatically higher than the prevalence reported among higher-income women in a national study in the late 1980s and early 1990s (one in 18). Furthermore, they point out that the condition remained common in the WIC sample for longer than the 4-6 weeks after delivery that it usually takes iron levels to return to normal. Although clinical guidelines call for screening at 4-6 weeks after delivery only for women considered to have a high risk of postpartum anemia (i.e., those who were anemic through the third trimester, who lost excessive amounts of blood during delivery or who had a multiple birth), the researchers conclude that this protocol is inadequate for low-income populations. Rather, they emphasize the importance of screening all low-income women. Furthermore, they recommend that "given the magnitude of the problem..., the continuation of iron supplementation after delivery until women are screened at their first postpartum medical visit may be warranted."--D. Hollander

REFERENCE

1. Bodnar LM et al., High prevalence of postpartum anemia among low-income women in the United States, American Journal of Obstetrics and Gynecology, 2001, 185(2):438-443.